Thin film forming device, method of forming a thin film, and self-light-emitting device

ABSTRACT

Measure of forming an EL layer by selectively depositing through evaporation a material for forming the EL layer at a desired location is provided. When a material for forming an EL layer is deposited, a mask ( 113 ) is provided between a sample boat ( 111 ) and a substrate ( 110 ). By applying voltage to the mask ( 113 ), the direction of progress of the material for forming the EL layer is controlled to be selectively deposited at a desired location.

This application is a continuation of U.S. application Ser. No.10/790,972, filed on Mar. 2, 2004 which is a divisional of U.S.application Ser. No. 09/798,608 filed Mar. 2, 2001 (now U.S. Pat. No.6,699,739 issued Mar. 2, 2004).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a self-light-emitting device having anEL element formed on an insulator and structured to have an anode, acathode, and a light-emitting organic material that provides electroluminescence (hereinafter referred to as an organic EL material)sandwiched therebetween, an electric apparatus having such aself-light-emitting device as a display unit (a display or a monitor),and a method of manufacturing thereof. It is to be noted that such an ELdisplay device is sometimes referred to as an OLED (organic lightemitting diode).

2. Description of the Related Art

These days, display devices using EL elements as self-light-emittingdevices utilizing electro luminescence of a light-emitting organicmaterial (EL display devices) are actively developed. Since an ELdisplay device is of a self-light-emitting type, unlike the case of aliquid crystal display device, no backlight is necessary. Further, sincethe view angle is wide, an EL display device is expected to be promisingas a display unit of an electric apparatus.

EL display devices are broken down into two: a passive type (simplematrix type); and an active type (active matrix type), both of whichhave been actively developed. Particularly, active matrix EL displaydevices are attracting attention these days. With regard to EL materialsto be an EL layer which can be the to be the center of an EL element,low molecular weight organic EL materials and macromolecular (polymer)organic EL materials have been studied.

A film of an EL material is formed by ink jetting, evaporation, spincoating, or the like. With regard to evaporation, the location of filmformation is controlled using a mask. Here, there is a problem in thatthe EL material does not pass through the mask, but instead is depositedon the mask.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and an objectof the present invention is therefore to provide means for selectivelyforming a film of an EL material without a waste by evaporation wherethe EL material is controlled by an electric field using a mask. Anotherobject of the present invention is to improve the accuracy ofcontrolling the location of film formation. Still another object of thepresent invention is to provide a self-light-emitting device using suchmeasures and a method of manufacturing thereof. Yet another object ofthe present invention is to provide an electric apparatus having such aself-light-emitting device as a display unit.

In order to attain the above objects, according to the presentinvention, voltage is applied to the mask and a pixel electrode on whichfilm formation is to be performed.

According to the present invention, the EL material is provided in asample boat. By vaporizing and charging the EL material, it isdischarged from an opening of the sample boat due to the vaporization,and, before it reaches a substrate, its direction of progress iscontrolled by the electric field generated by voltage applied to themask, and thus, the location of deposition of the EL material can becontrolled.

A plurality of masks may be used. For instance, an electric field isgenerated by voltages applied to a first mask and a second maskrespectively, thereby controlling the direction of progress of the ELmaterial and controlling the location where it is deposited.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are diagrams showing a method of depositing byevaporation an organic EL material according to the present invention;

FIG. 2 is a diagram illustrating the structure in section of a pixelportion;

FIGS. 3A to 3C are diagrams illustrating the structure of the pixelportion and the top view thereof;

FIGS. 4A to 4E are diagrams illustrating a process of manufacturing anEL display device;

FIGS. 5A to 5D are diagrams illustrating the process of manufacturing anEL display device;

FIGS. 6A to 6C are diagrams illustrating the process of manufacturing anEL display device;

FIGS. 7A and 7B are diagrams illustrating the structure in section of aTFT in a pixel portion of an EL display device;

FIGS. 8A and 8B are diagrams illustrating the structure in section of aTFT in a pixel portion of an EL display device;

FIG. 9 is a diagram illustrating an outward appearance of an EL displaydevice;

FIG. 10 is a diagram illustrating a circuit block structure of an ELdisplay device;

FIGS. 11A and 11B are diagrams showing the structure in section of anactive matrix EL display device;

FIGS. 12A and 12B are diagrams each showing a pattern of deposition ofan organic EL material by evaporation;

FIGS. 13A and 13B are diagrams each showing a pattern of a mask;

FIG. 14 is a diagram illustrating the structure in section of a passiveEL display device;

FIGS. 15A to 15F are diagrams showing specific examples of an electricapparatus;

FIGS. 16A and 16B are diagrams showing specific examples of the electricapparatus; and

FIGS. 17A and 17B are diagrams illustrating a method of depositing anorganic EL material by evaporation according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment mode of the present invention is now described withreference to FIGS. 1A and 1B.

FIG. 1A schematically illustrates how a film of an EL material is formedin accordance with the present invention. In FIG. 1A, a pixel electrodeon a substrate 110 is connected to a ground potential. A sample boat 111has an EL material contained therein.

It is to be noted that, when a red EL layer is formed, the sample boat111 contains an EL material that emits red light (hereinafter referredto as a red EL material). When a green EL layer is formed, the sampleboat 111 contains an EL material that emits green light (hereinafterreferred to as a green EL material). When a blue EL layer is formed, thesample boat 111 contains an EL material that emits blue light(hereinafter referred to as a blue EL material).

According to the present invention, the EL material in the sample boat111 is vaporized and discharged by resistance heating due to anelectrode 120. The EL material becomes, when discharged, negativelycharged particles due to negative voltage applied to an electrode 112.The negatively charged particles pass through gaps of a mask 113 formedof a conductive material, and are deposited on the pixel electrode onthe substrate 110. An insulator is provided between the electrodes 112and 120, to which different voltages are applied.

It is to be noted that, as illustrated in FIG. 1B that is an enlargedview of 117, the direction of progress of the EL material is controlledby blocking portions 118 of the mask 113 when the EL material passesthrough the mask 113. In the mask 113, the blocking portions 118 are aplurality of conductive wires arranged in parallel with one another(stripe-like) formed of a conductive material such as copper, iron,aluminum, tantalum, titanium, or tungsten, a mesh-like structure, or aplate-like structure. The EL material in a vapor state repels anelectric field generated by negative voltage applied to the blockingportions 118, and thus, passes through the gaps between the blockingportions 118 to be deposited on the substrate.

Though illustrated in FIGS. 1A and 1B is a case where the section of ablocking portion 118 is circular, the present invention is not limitedthereto, and the section may be rectangular, oval or polygonal.

It is to be noted that voltage for giving the EL material in a vaporstate a potential that causes the EL material to repel the blockingportions 118 of the mask 113 is applied to the blocking portions 118 ofthe mask 113. This allows the EL material to pass through the gapsbetween the blocking portions 118 of the mask 113. It is to be notedthat, here, the EL material in a vapor state is charged by the electricfield generated by the electrode 112 to which negative voltage isapplied, while negative voltage is applied by an electrode 115 to theblocking portions 118 of the mask 113 to generate an electric field.These make the charged particles of the EL material in a vapor stateelectrically repel the blocking portions to pass through gaps betweenthe blocking portions.

By making a structure as illustrated in FIG. 1A and by appropriatelycontrolling the negative voltage applied to the blocking portions 118 inthe range of several equal to or more than 10 V and equal to or lessthan 10 kV, the location of deposition can be controlled with highaccuracy.

It is to be noted that the distance between the mask 113 and thesubstrate, the distance between the blocking portions 118, and the likecan be appropriately set by those who implement the present invention.For example, the distance between the blocking portions 118 may be apixel pitch of the pixel electrode formed over the substrate.

Further, in order to accurately position the mask 113, the mask 113 maybe formed by laminating two conductive plates and cutting themsimultaneously by an electron discharge method to form slit-like orcircular holes.

Further, though a case where one mask is used is described here, voltagemay be applied to two or more masks to control the direction oftrajectory of the EL material. Further, voltage may be applied to acombination of two or more masks in one plane to control the directionof trajectory of the EL material in a vapor state.

First, a red EL material is put in the sample boat 111 and is depositedby evaporation to form a stripe-like red EL layer on a pixel.

After the mask is moved in a direction of an arrow k by one pixelcolumn, a green EL material is deposited by evaporation from the sampleboat 111 to form a green EL layer. The mask is further moved in thedirection of the arrow k by one pixel column, deposition by evaporationis made in a similar way, and a blue EL layer is formed.

In other words, by depositing in three installments pixel columnsemitting red, green, and blue light, respectively, as the mask is movedin the direction of the arrow k, stripe-like EL layers of three colorsare formed. It is to be noted that the thickness of the EL layers formedhere is preferably 10 nm to 10 μm.

A pixel column as used herein refers to a column of pixels formed bybeing partitioned by banks 119. The banks 119 are formed over sourcewirings of the pixel columns so as to be banks filling gaps between thepixel columns. In other words, since the banks partition the pixelcolumns, EL layers can be formed in the respective pixel columns onpixels while distinguishing one pixel column from its adjacent pixelcolumn. Therefore, a pixel column may also be represented as a pluralityof pixels lined up along a source wiring. Though a case where the banksare formed over the source wirings is described here, the banks may beformed over gate wirings. In that case, a plurality of pixels lined upalong a gate wiring is referred to as a pixel column.

Therefore, a pixel portion (not shown) on pixel electrodes may beregarded as an aggregate of a plurality of pixel columns partitioned bystripe-like banks provided over a plurality of source wirings or aplurality of gate wirings. The pixel portion on the pixel electrodes mayalso be regarded as constitution of pixel columns having stripe-like ELlayers emitting red light formed thereon, pixel columns havingstripe-like EL layers emitting green light formed thereon, and pixelcolumns having stripe-like EL layers emitting blue light formed thereon.

Since the stripe-like banks are provided over the plurality of sourcewirings or the plurality of gate wirings, practically, the pixel portionmay also be regarded as an aggregate of a plurality of pixel columnspartitioned by the plurality of source wirings or the plurality of gatewirings actually.

Further, in this embodiment mode, it is preferable to apply voltage to apixel electrode (an anode) formed on the substrate 110 to generate anelectric field that further controls the EL material in a vapor statehaving passed through the mask and selectively deposits the EL materialin a vapor state at desired locations.

Further, by applying negative voltage by an electrode 114 to inner sidesurfaces of an evaporation chamber 121 which has therein the sample boat111, the mask 113, and the substrate 110, the negatively charged ELmaterial in a vapor state can be made to repel the inner side surfacesof the evaporation chamber, and, therefore, the EL material in a vaporstate can be deposited without adhering to the inner side surfaces ofthe evaporation chamber.

Embodiment 1

In this embodiment, a method of controlling an EL material vaporized ina sample boat (hereinafter referred to as an EL material in a vaporstate) using an electric field and forming the film on a substrate isdescribed with reference to FIGS. 1A and 1B.

In FIGS. 1A and 1B, a reference numeral 110 denotes a substrate. Asample boat 111 has a material for an EL layer.

It is to be noted that, when a red EL layer is to be formed, the sampleboat 111 contains an EL material that emits red light (hereinafterreferred to as a red EL material). When a green EL layer is to beformed, the sample boat 111 contains an EL material that emits greenlight (hereinafter referred to as a green EL material). When a blue ELlayer is to be formed, the sample boat 111 contains an EL material thatemits blue light (hereinafter referred to as a blue EL material).

It is to be noted that, in this embodiment, Alq as a host material witha red fluorescent pigment DCM doped therein is used as the red ELmaterial for forming a red EL layer, Alq that is a complex of aluminumand 8-hydroxyquinoline is used as the green EL material for forming agreen-light-emitting EL layer, and a complex of zinc and benzoxazole(Zn(oxz)₂) is used as the blue EL material for forming ablue-light-emitting EL layer.

It is to be noted that the above EL materials are merely examples andother conventional EL materials may also be used. Further, though the ELmaterials are selected to emit red, green, and blue light, the presentinvention is not limited thereto and colors such as yellow, orange, andgray may also be used.

In this embodiment, first, the sample boat contains the red EL material.After a red EL layer is formed on the substrate, the sample boat nowcontaining the green EL material is used to form a green EL layer on thesubstrate. Then, finally, the sample boat now containing the blue ELmaterial is used to form a blue EL layer on the substrate.

By depositing through evaporation of the red, green, and blue ELmaterials in three installments as described in the above, EL layers canbe formed.

The EL material in each color is vaporized in the sample boat byresistance heating using an electrode 120. When the EL material isdischarged from the sample boat 111, it is charged by the electric fieldgenerated by an electrode 112. Here, the EL material is discharged byhigher kinetic energy obtained by the vaporization to reach a mask 113.

Since voltage is applied to the mask 113, an electric field is generatedaround the mask 113. The material in a vapor state for the EL layerhaving reached the mask 113 is, after being controlled by the electricfield generated by the mask 113, passes through the mask 113 to bedeposited on the substrate 110.

By depositing through evaporation of the red EL material in the sampleboat 111, a stripe-like red EL layer is formed on pixels. Here, the maskis moved in a direction of an arrow k by one pixel column, and in asimilar way, a green EL material is deposited through evaporation fromthe sample boat 111 to form a green EL layer next to the red EL layer.The mask is further moved in the direction of the arrow k by one pixelcolumn and the blue EL material is deposited through evaporation fromthe sample boat 111 to form a blue EL layer next to the green EL layer.In other words, by depositing in three installments pixel columnsemitting red, green, and blue light, respectively, as the mask is movedin the direction of the arrow k, stripe-like EL layers of three colorsare formed. It is to be noted that the thickness of the EL layers formedhere is preferably 100 nm to 1 μm.

It is to be noted that a pixel column as used herein refers to a columnof pixels formed by being partitioned by banks 119 that are formed oversource wirings. Therefore, a pixel column may also be represented as aplurality of pixels lined up along a source wiring. Though a case wherethe banks are formed over the source wirings is described here, thebanks may be formed over gate wirings. In that case, a plurality ofpixels lined up along a gate wiring is referred to as a pixel column.

Therefore, a pixel portion (not shown) may be regarded as an aggregateof a plurality of pixel columns partitioned by stripe-like banksprovided over a plurality of source wirings or a plurality of gatewirings. The pixel portion may also be regarded as constitution of pixelcolumns having stripe-like EL layers emitting red light formed thereon,pixel columns having stripe-like EL layers emitting green light formedthereon, and pixel columns having stripe-like EL layers emitting bluelight formed thereon.

Since the stripe-like banks are provided over the plurality of sourcewirings or the plurality of gate wirings, practically, the pixel portionmay also be regarded as an aggregate of a plurality of pixel columnspartitioned by the plurality of source wirings or the plurality of gatewirings actually.

Further, it is preferable to apply voltage to a pixel electrode (ananode) formed on the substrate 110 to generate an electric field thatfurther controls the EL material in a vapor state having passed throughthe mask and selectively deposits the EL material in a vapor state atdesired locations.

Embodiment 2

FIG. 2 is a sectional view of a pixel portion of an EL display deviceaccording to this embodiment. FIG. 3A is a top view of the pixelportion, and FIG. 3B illustrates its circuit structure. Actually, aplurality of pixels are arranged to be matrix-like to form a pixelportion (an image display portion). It is to be noted that FIG. 2 is asectional view taken along the line A-A′ in FIG. 3A. Thus, since commonnumeralss are used in FIG. 2 and FIGS. 3A, 3B, and 3C, reference may besuitably made to the both drawings. Two pixels are illustrated in thetop view of FIG. 3A, and the two pixels are of the same structure.

In FIG. 2, reference numerals 11 and 12 denote a substrate and aninsulating film to be a base (hereinafter referred to as a base film),respectively. As the substrate 11, glass, glass ceramics, quartz,silicon, ceramics, metal, or plastic can be used.

Especially when a substrate containing movable ions or a conductivesubstrate is used, it is effective to use the base film 12, while aquartz substrate may not be provided with the base film 12. As the basefilm 12, an insulating film containing silicon may be used. It is to benoted that the term “an insulating film containing silicon” hereinrefers to an insulating film containing a predetermined percentage ofsilicon, and oxygen or nitrogen such as a silicon oxide film, a siliconnitride film, or a silicon oxynitride film (represented asSiO_(x)N_(y)).

It is effective to radiate heat generated by the TFTs by making the basefilm 12 have a heat radiating effect, in order to prevent deteriorationof the TFTs and deterioration of the EL element. Any conventionalmaterial may be used to make the base film 12 have a heat radiatingeffect.

Here, two TFTs are formed in a pixel. A TFT 201 for switching is formedof an n-channel TFT while a TFT 202 for controlling electric current isformed of a p-channel TFT.

However, it is not necessary to limit the TFT for switching to be ann-channel TFT and to limit the TFT for controlling electric current tobe a p-channel TFT. The TFT for switching may be a p-channel TFT and theTFT for controlling electric current may be an n-channel TFT, or bothTFTs may be formed of n-channel TFTs, or both TFTs may be formed ofp-channel TFTs.

The TFT 201 for switching is formed so as to have an active layerincluding a source region 13, a drain region 14, LDD regions 15 a to 15d, a heavily doped impurity region 16, and channel forming regions 17 aand 17 b, as well as a gate insulating film 18, gate electrodes 19 a and19 b, a first interlayer insulating film 20, a source wiring 21, and adrain wiring 22.

As illustrated in FIGS. 3A to 3C, the TFT 201 for switching has adouble-gate structure where the gate electrodes 19 a and 19 b areelectrically connected to each other through a gate wiring 211 formed ofa different material (a material having a lower resistance than that ofthe gate electrodes 19 a and 19 b). Of course, instead of the doublegate structure, the TFT 201 for switching may have a single-gatestructure or a multi-gate structure (a structure including an activelayer having two or more serially connected channel forming regions)such as a triple-gate structure. A multi-gate structure is veryeffective in decreasing the off current value. Here, by making theswitching element 201 of the pixel have the multi-gate structure, aswitching element having a small off current value is realized.

The active layer is formed of a semiconductor film containing a crystalstructure. The active layer may be a single crystal semiconductor film,a polycrystalline semiconductor film, or a microcrystallinesemiconductor film. The gate insulating film 18 may be an insulatingfilm containing silicon. As the gate electrodes, the source wiring, andthe drain wiring, any conductive film may be used.

Further, in the TFT 201 for switching, the LDD regions 15 a to 15 d areprovided so as not to overlap the gate electrodes 19 a and 19 b throughthe gate insulating film 18. Such a structure is very effective indecreasing the off current value.

It is to be noted that to provide an offset region (a region which isformed of a semiconductor layer of the same composition as that of thechannel forming region and to which gate voltage is not applied) betweenthe channel forming region and the LDD regions is further preferable indecreasing the off current value. Further, in the case of a multi-gatestructure having two or more gate electrodes, the heavily doped impurityregion provided between elements of the channel forming region iseffective in decreasing the off current value.

The TFT 202 for controlling electric current is formed so as to have anactive layer including a source region 31, a drain region 32, and achannel forming region 34, as well as the gate insulating film 18, agate electrode 35, the first interlayer insulating film 20, a sourcewiring 36, and a drain wiring 37. It is to be noted that, though thegate electrode 35 is of a single-gate structure in the figure, it may beof a multi-gate structure.

As illustrated in FIG. 2, a drain of the TFT 201 for switching isconnected to a gate of the TFT 202 for controlling electric current.More specifically, the gate electrode 35 of the TFT 202 for controllingelectric current is electrically connected to the drain region 14 of theTFT 201 for switching through the drain wiring (which may be the to be aconnection wiring) 22. The source wiring 36 is connected to a powersupply line 212.

The TFT 202 for controlling electric current is an element forcontrolling the amount of electric current to flow in an EL element 203.However, taking into consideration the deterioration of the EL element203, it is not preferable that a large amount of electric current flowsin the EL element 203. Therefore, in order to prevent an excess amountof electric current from flowing in the TFT 202 for controlling electriccurrent, it is preferable that the channel length (L) is designed to belongish. It is desirable that the channel length per pixel is 0.5 to 2μÅ (preferably 1 to 1.5 μÅ).

The length (width) of an LDD region formed in the TFT 201 for switchingmay be 0.5 to 3.5 μm, representatively 2.0 to 2.5 μm.

As illustrated in FIGS. 3A to 3C, the wiring including the gateelectrode 35 of the TFT 202 for controlling electric current overlapsthe power supply line 212 of the TFT 202 for controlling electriccurrent through the insulating film in a region denoted by 50. Here, astorage capacitor is formed in the region 50. A capacitor formed of asemiconductor film 51, an insulating film (not shown) as the same layeras the gate insulating film, and the power supply line 212 can be alsoused as a storage capacitor.

The storage capacitor 50 functions as a capacitor for storing voltageapplied to the gate electrode 35 of the TFT 202 for controlling electriccurrent.

Further, from the viewpoint of increasing the amount of flowableelectric current, it is also effective to increase the thickness of theactive layer (in particular, the channel forming region) of the TFT 202for controlling electric current (preferably 50 to 100 nm, and morepreferably 60 to 80 nm). On the contrary, with regard to the TFT 201 forswitching, from the viewpoint of decreasing the off current value, it isalso effective to decrease the thickness of the active layer (inparticular, the channel forming region) (preferably 20 to 50 nm, andmore preferably 25 to 40 n).

A first passivation film 38 is formed at the thickness of 10 nm to 10 μm(preferably 200 to 500 nm). As the material, an insulating filmcontaining silicon (especially, a silicon oxynitride film or a siliconnitride film is preferable) can be used.

A second interlayer insulating film (which may also be referred to as aplanarizing film) 39 is formed on the first passivation film 38 so as tocover the respective TFTs to level a level difference formed by theTFTs. As the second interlayer insulating film 39, an organic resin filmof such as a polyimide resin, a polyamide resin, an acrylic resin, orBCB (benzocyclobutene) is preferable. Of course, an inorganic film mayalso be used if it can perform sufficient planarization.

It is quite important to planarize, by the second interlayer film 39, alevel difference formed by the TFT. Since an EL layer to be formed lateris very thin, existence of a level difference may cause light emissionfailure. Therefore, it is preferable that planarization is performedprior to the formation of the pixel electrode in order to make as levelas possible the surface on which the EL layer is formed.

After a contact hole (an opening) is formed in the second interlayerinsulating film 39 and the first passivation film 38, a pixel electrode40 (corresponding to an anode of the EL element) of a transparentconductive film is formed so as to be connected at the formed opening tothe drain wiring 37 of the TFT 202 for controlling electric current.

According to this embodiment, as the pixel electrode, a conductive filmformed of a compound of indium oxide and tin oxide is used. A smallamount of gallium may be doped into the compound. Further, a compound ofindium oxide and zinc oxide, or a compound of zinc oxide and galliumoxide may be used.

After the pixel electrode is formed, banks of a resin material areformed. A bank a (41 a) and a bank b (41 b) are formed by, using resistmaterials, patterning organic resin films having different selectionratios. It is to be noted that, here, by etching the bank a (41 a) andthe bank b (41 b) after they are laminated, the shape illustrated inFIG. 2 can be formed due to the difference in the etching rate. It is tobe noted that, here, the relationship of (the etching rate of the resinforming the bank a)>(the etching rate of the resin forming the bank b)is established. The bank a (41 a) and the bank b (41 b) are formed to bestripe-like between the pixels as illustrated in FIG. 3C. It is to benoted that, preferably, h1 in FIG. 3C is 0.5 to 3 μm and larger inthickness than a film formed by laminating an EL layer, a cathode, and aprotective electrode. Though the banks are formed along the sourcewiring 21 in this embodiment, they may be formed along the gate wiring211.

Then, an EL layer 42 is formed by the thin film forming method asdescribed with reference to FIGS. 1A and 1B. It is to be noted that,though only one pixel is illustrated here, actually, EL layerscorresponding to R (red), G (green), and B (blue), respectively, areformed as illustrated in FIGS. 1A and 1B.

First, an EL material contained in the sample boat 111 is vaporized byresistance heating using the electrode 120. Just as the EL material in avapor state is discharged from the sample boat 111, under the influenceof an electric field generated by the electrode 112 attached at anopening of the sample boat 111, the EL material in a vapor state ischarged to be charged particles. The direction of progress of thesecharged particles is controlled when they pass through the mask 113 byan electric field around the mask 113 generated by voltage applied toblocking portions 118.

It is to be noted that an electrode may be provided between the sampleboat 111 and the mask 113 to control the charge of the EL material in avapor state discharged from the sample boat 111 by an electric fieldgenerated by the electrode.

As a result, the vapor EL material passes through gaps between theblocking portions 118 to be deposited on the surface of the substratewhere it is to be formed.

It is to be noted that blocking portions of a mask as used in thisspecification refer to portions formed of a conductive material of themask, and examples of the conductive material include titanium,tantalum, tungsten, and aluminum. Further, openings in the mask refer togaps between the blocking portions.

Further, a surface where an EL material is to be formed as used in thisspecification refers to a part of the surface of a pixel electrode or anorganic film where a thin film is to be formed.

The voltage applied to the mask is equal to or more than several 10 Vand equal to or less than 10 kV, preferably 10 V to 1 kV. Those whoimplement the present invention may appropriately set the voltages tothe respective electrodes in this range.

In this embodiment, first, by vaporizing and depositing the red ELmaterial contained in the sample boat 111, a pixel column that emits redlight is formed on the pixels. Then, after the mask is moved in alateral direction (a direction shown by an arrow k), the green ELmaterial contained in the sample boat 111 is deposited throughevaporation to form a pixel column that emits green light. The mask isfurther moved in the lateral direction (the direction shown by the arrowk) and the blue EL material contained in the sample boat 111 isdeposited through evaporation to form a pixel column that emits bluelight.

It is to be noted that the sample boat 111 having the EL materialcontained therein may be changed every time when the kind of the ELmaterial is changed, or, alternatively, only the EL material to be usedmay be changed without changing the sample boat 111.

Further, the sample boat 111 and the mask described here may beseparately provided, or, alternatively, may be integrally formed as onedevice.

As described in the above, by depositing through evaporation in threeinstallments the pixel columns emitting red, green, and blue light,respectively, as the mask is moved, the stripe-like EL layers of thethree colors are formed.

As the EL materials to be the EL layers, low molecular weight materialsmay be used. Representative low molecular weight materials for the ELmaterials include tris(8-quinolinolate) aluminum complex (Alq) andbis(benzoquinolinolate) beryllium complex (BeBq).

It is to be noted that, in this embodiment, Alq as a host material witha red fluorescent pigment DCM doped therein is used as the EL materialfor forming a red EL layer, Alq that is a complex of aluminum and8-hydroxyquinoline is used as the green EL layer, and a complex of zincand benzoxazole (Zn(oxz)₂) is used as the blue EL layer.

However, the above are merely examples of the EL materials that can beused as the EL layers of this embodiment, and the present invention isby no means limited thereto.

In other words, macromolecular organic EL materials that are not listedherein may be used with a coating method and the EL layers may be formedusing macromolecular materials in addition to the low molecular weightmaterials.

Further, when the EL layer 42 is formed, since the EL layer is easilydeteriorated by the existence of moisture and oxygen, it is preferablethat the processing be performed in an inert gas such as nitrogen orargon which contains little moisture and oxygen.

After the EL layer 42 is formed as in the above, a cathode 43 formed ofa light-shielding conductive film, a protective electrode 44, and asecond passivation film 45 are formed. In this embodiment, a conductivefilm formed of MgAg is used as the cathode 43, a conductive film formedof aluminum is used as the protective electrode 44, and a siliconnitride film with a thickness of 10 nm to 10 μm (preferably 200 to 500nm) is used as the second passivation film 45.

It is to be noted that, as described in the above, since the EL layer iseasily affected by heat, the cathode 43 and the second passivation film45 are desirably formed at a temperature as low as possible (preferablyin the temperature range of from room temperature to 120° C.).Therefore, in this case, plasma enhanced CVD, vacuum evaporation, orspin coating is a preferable film forming method.

The device in this stage of completion is referred to as an activematrix substrate. An opposing substrate (not shown) is provided so as tobe opposed to the active matrix substrate. In this embodiment, a glasssubstrate is used as the opposing substrate. It is to be noted that, asthe opposing substrate, a substrate formed of plastic or ceramics mayalso be used.

The active matrix substrate and the opposing substrate are adhered toeach other by a sealing material (not shown) to form a sealed space (notshown). In this embodiment, the sealed space is filled with argon gas.Of course, a desiccant such as barium oxide or an antioxidant can bedisposed inside the sealed space.

Further, the structure of this embodiment can be freely combined withthe structure of Embodiment 1.

Embodiment 3

Here, a method of forming a bank consisting of the bank a and the bank billustrated in FIG. 3C is described. Both the bank a and the bank b areof positive type.

First, after a pixel electrode is formed, an organic resin film ofmelamine resin to be the bank a is formed. A dye is mixed in themelamine resin to make the organic resin film have a function as anantireflection film. These may be used after being dissolved in asolvent such as dimethylacetamide. It is to be noted that, in selectingthe dye, it is necessary to select a dye having emission spectrum nearthe spectrum of light used in exposure.

Then, a polyimide film is laminated on the melamine resin film. Here,photosensitive polyimide or a novolac resin may be used instead ofpolyimide. This is to form the bank b.

It is to be noted that the organic resin film formed here has twolayers. The organic resin film is then exposed to light to be patterned.As the developer for the patterning, a water-soluble one is preferablyused. In this embodiment, tetramethyl ammonium hydroxide may be used,since it is water-soluble and alkaline, and thus, suitable for thisembodiment. However, the developer is not limited thereto, and otherconventional developers may also be used.

By developing using the developer, the bank a and the bank b are shapedas illustrated in FIG. 3C. This is because, by mixing the dye in thebank a, its strength against exposure has changed, and thus, is etchedisotropically by the developer. It is to be noted that h2 shown here ispreferably 0.5 to 3 μm.

It is to be noted that the bank a and the bank b are not limited to thelaminated structure of the organic resin film as described above. Thebanks may be formed such that the bank b is formed of an organic resinfilm such as a polyimide resin, a polyamide resin, or a photosensitiveresin after the bank a is formed of an inorganic film such as siliconoxide or silicon nitride, or the material used for the bank a and thematerial used for the bank b may be reversed.

It is to be noted that the structure of this embodiment can be freelycombined with the structures of Embodiments 1 and 2.

Embodiment 4

A method of simultaneously forming a pixel portion and TFTs of a drivercircuit portion formed in the periphery of the pixel portion, isexplained here with reference to FIGS. 4 to 6. Note that in order tosimplify the explanation, a CMOS circuit is shown as a basic circuit forthe driver circuits.

First, as shown in FIG. 4A, a base film 301 is formed with a 300 nmthickness on a glass substrate 300. As the base film 301, a siliconoxynitride film having a thickness of 100 nm is laminated on a siliconoxynitride film having a thickness of 200 nm in this embodiment. It isgood to set the nitrogen concentration at between 10 and 25 wt % in thefilm contacting the glass substrate 300. Needless to say, elements canbe formed on the quartz substrate without providing the base film.

Next, an amorphous silicon film (not shown in the figures) is formedwith a thickness of 50 nm on the base film 301 by a known depositionmethod. Note that it is not necessary to limit this to the amorphoussilicon film, and a semiconductor film containing an amorphous structure(including a microcrystalline semiconductor film) may be used. Inaddition, a compound semiconductor film containing an amorphousstructure, such as an amorphous silicon-germanium film, may also beused. Further, the film thickness may be made from 20 to 100 nm.

The amorphous silicon film is then crystallized by a known method,forming a crystalline silicon film (also referred to as apolycrystalline silicon film or a poly-crystalline silicon film) 302.Thermal crystallization using an electric furnace, laser annealingcrystallization using a laser, and lamp annealing crystallization usingan infrared lamp are included in known crystallization methods.Crystallization is performed in this embodiment using an excimer laserlight which uses XeCl gas.

Note that pulse emission type excimer laser light formed into a linearshape is used in this embodiment, but a rectangular shape may also beused, and continuous emission argon laser light and continuous emissionexcimer laser light can also be used.

In this embodiment, although the crystalline silicon film is used as anactive layer of the TFT, it is also possible to use an amorphous siliconfilm. Further, it is possible to form the active layer of the TFT forswitching, in which there is a necessity to reduce the off current, bythe amorphous silicon film, and to form the active layer of the currentcontrol TFT by the crystalline silicon film. Electric current flows withdifficulty in the amorphous silicon film because the carrier mobility islow, and the off current does not easily flow. In other words, the mostcan be made of the advantages of both the amorphous silicon film,through which current does not flow easily, and the crystalline siliconfilm, through which current easily flows.

Next, as shown in FIG. 4B, a protective film 303 is formed on thecrystalline silicon film 302 made of a silicon oxide film having athickness of 130 nm. This thickness may be chosen within the range of100 to 200 nm (preferably between 130 and 170 nm). Furthermore, otherfilms such as insulating films containing silicon may also be used. Theprotective film 303 is formed so that the crystalline silicon film isnot directly exposed to plasma during addition of an impurity, and sothat it is possible to have delicate concentration control of theimpurity.

Resist masks 304 a and 304 b are then formed on the protective film 303,and an impurity element which imparts n-type conductivity (hereafterreferred to as an n-type impurity element) is added via the protectivefilm 303. Note that elements residing in periodic table group 15 aregenerally used as the n-type impurity element, and typically phosphorousor arsenic can be used. Note that a plasma doping method is used, inwhich phosphine (PH₃) is plasma excited without separation of mass, andphosphorous is added at a concentration of 1×10¹⁸ atoms/cm³ in thisembodiment. An ion implantation method, in which separation of mass isperformed, may also be used, of course.

The dose amount is regulated so that the n-type impurity element iscontained in n-type impurity regions 305 formed in accordance with thisstep at a concentration of 2×10¹⁶ to 5×10¹⁹ atoms/cm³ (typically between5×10⁷ and 5×10¹⁸ atoms/cm³).

Next, as shown in FIG. 4C, the protective film 303, resist masks 304 aand 304 b are removed, and an activation of the added periodic tablegroup 15 elements is performed. A known technique of activation may beused as the means of activation, but activation is done in thisembodiment by irradiation of excimer laser light. Of course, a pulseemission type excimer laser and a continuous emission type excimer lasermay be used, and it is not necessary to limit on the use of excimerlaser light. The goal is the activation of the added impurity element,and it is preferable that irradiation is performed at an energy level atwhich the crystalline silicon film does not melt. Note that the laserirradiation may also be performed with the protective film 303 in place.

The activation by heat treatment may also be performed along withactivation of the impurity element by laser light. When activation isperformed by heat treatment, considering the heat resistance of thesubstrate, it is good to perform heat treatment at a temperature ofabout 450 to 550° C.

A boundary portion (connecting portion) with end portions of the n-typeimpurity region 305, namely region, in which the n-type impurity elementis not added, on the periphery of the n-type impurity region 305, is notadded, is delineated by this process. This means that, at the point whenthe TFTs are later completed, extremely good connections can be formedbetween LDD regions and channel forming regions.

Unnecessary portions of the crystalline silicon film are removed next,as shown in FIG. 4D, and island-like semiconductor films (hereafterreferred to as active layers) 306 to 309 are formed.

Then, as shown in FIG. 4E, a gate insulating film 310 is formed,covering the active layers 306 to 309. An insulating film containingsilicon is formed to a thickness of 10 to 200 nm, preferably between 50and 150 nm, as the gate insulating film 310. A single layer structure ora lamination structure may be used. A 110 nm thick silicon oxynitridefilm is used in this embodiment.

Thereafter, a conductive film having a thickness of 200 to 400 nm isformed and patterned to form gate electrodes 311 to 315. Respective endportions of these gate electrodes 311 to 315 may be tapered. In thepresent embodiment, the gate electrodes and wirings (hereinafterreferred to as the gate wirings) electrically connected to the gateelectrodes for providing lead wires are formed of different materialsfrom each other. More specifically, the gate wirings are made of amaterial having a lower resistivity than the gate electrodes. Thus, amaterial enabling fine processing is used for the gate electrodes, whilethe gate wirings are formed of a material that can provide a smallerwiring resistance but is not suitable for fine processing. It is ofcourse possible to form the gate electrodes and the gate wirings withthe same material.

Although the gate electrode can be made of a single-layered conductivefilm, it is preferable to form a lamination film with two, three or morelayers for the gate electrode if necessary. Any known conductivematerials can be used for the gate electrode. It should be noted,however, that it is preferable to use such a material that enables fineprocessing, and more specifically, a material that can be patterned witha line width of 2 μm or less.

Typically, it is possible to use a film made of an element selected fromtantalum (Ta), titanium (Ti), molybdenum (Mo), tungsten (W), chromium(Cr), and silicon (Si), a film of nitride of the above element(typically a tantalum nitride film, a tungsten nitride film, or atitanium nitride film), an alloy film of combination of the aboveelements (typically Mo—W alloy, Mo—Ta alloy), or a silicide film of theabove element (typically a tungsten silicide film or titanium silicidefilm). Of course, the films may be used as a single layer or a laminatelayer.

In this embodiment, a laminate film of a tantalum nitride (TaN) filmhaving a thickness of 50 nm and a tantalum (Ta) film having a thicknessof 350 nm is used. This may be formed by a sputtering method. When aninert gas of Xe, Ne or the like is added as a sputtering gas, filmpeeling due to stress can be prevented.

The gate electrode 312 is formed at this time so as to overlap andsandwich a portion of the n-type impurity regions 305 and the gateinsulating film 310. This overlapping portion later becomes an LDDregion overlapping the gate electrode. Further the gate electrodes 313and 314 appears two electrodes by a cross sectional view, practically,they are connected each other electrically.

Next, an n-type impurity element (phosphorous in this embodiment) isadded in a self-aligning manner with the gate electrodes 311 to 315 asmasks, as shown in FIG. 5A. The addition is regulated so thatphosphorous is added to impurity regions 316 to 323 thus formed at aconcentration of 1/10 to ½ that of the n-type impurity region 305(typically between ¼ and ⅓). Specifically, a concentration of 1×10¹⁶ to5×10¹⁸ atoms/cm³ (typically 3×10¹⁷ to 3×10⁸ atoms/cm³) is preferable.

Resist masks 324 a to 324 d are formed next, with a shape covering thegate electrodes etc., as shown in FIG. 5B, and an n-type impurityelement (phosphorous is used in this embodiment) is added, formingimpurity regions 325 to 329 containing high concentration ofphosphorous. Ion doping using phosphine (PH₃) is also performed here,and is regulated so that the phosphorous concentration of these regionsis from 1×10²⁰ to 1×10²¹ atoms/cm³ (typically between 2×10²⁰ and 5×10²¹atoms/cm³).

A source region or a drain region of the n-channel type TFT is formed bythis process, and in the TFT for switching, a portion of the n-typeimpurity regions 319 to 321 formed by the process of FIG. 5A isremained. These remaining regions correspond to the LDD regions 15 a to15 d of the TFT for switching 201 in FIG. 5.

Next, as shown in FIG. 5C, the resist masks 324 a to 324 d are removed,and a new resist mask 332 is formed. A p-type impurity element (boron isused in this embodiment) is then added, forming impurity regions 333 to336 containing boron at high concentration. Boron is added here to formimpurity regions 333 to 336 at a concentration of 3×10²⁰ to 3×10²¹atoms/cm³ (typically between 5×10²⁰ and 1×10²¹ atoms/cm³) by ion dopingusing diborane (B₂H₆).

Note that phosphorous has already been added to the impurity regions 333to 336 at a concentration of 1×10²⁰ to 1×10²¹ atoms/cm³, but boron isadded here at a concentration of at least not less than three times thatof the phosphorous. Therefore, the n-type impurity regions alreadyformed completely invert to p-type, and function as p-type impurityregions.

Next, after removing the resist mask 332, the n-type and p-type impurityelements added to the active layer at respective concentrations areactivated. Furnace annealing, laser annealing or lamp annealing can beused as a means of activation. In this embodiment, heat treatment isperformed for 4 hours at 550° C. in a nitrogen atmosphere in an electricfurnace.

At this time, it is important to eliminate oxygen from the surroundingatmosphere as much as possible. This is because when even only a smallamount of oxygen exists, an exposed surface of the gate electrode isoxidized, which results in an increased resistance and later makes itdifficult to form an ohmic contact with the gate electrode. Accordingly,the oxygen concentration in the surrounding atmosphere for theactivation process is set at 1 ppm or less, preferably at 0.1 ppm orless.

After the activation process is completed, the gate wiring 337 having athickness of 300 nm is formed as shown in FIG. 5D. As a material for thegate wiring 337, metal containing aluminum (Al) or copper (Cu) as itsmain component (occupied 50 to 100% in the composition) can be used. Asshown in FIG. 3, the gate wiring 211 is arranged to provide electricalconnection for the gate electrodes 19 a and 19 b (corresponding to thegate electrodes 313 and 314 in FIG. 4E) of the switching TFT.

The above-described structure can allow the wiring resistance of thegate wiring to be significantly reduced, and therefore, an image displayregion (pixel portion) with a large area can be formed. Morespecifically, the pixel structure in accordance with the presentembodiment is advantageous for realizing an EL display device having adisplay screen with a diagonal size of 10 inches or larger (or 30 inchesor larger.)

A first interlayer insulating film 338 is formed next, as shown in FIG.6A. A single layer insulating film containing silicon is used as thefirst interlayer insulating film 338, while a lamination film, which isa combination of insulating films including two or more kinds ofsilicon, may be used. Further, a film thickness of between 400 nm and1.5 μm may be used. A lamination structure of a silicon oxide filmhaving a thickness of 800 nm on a silicon oxynitride film having athickness of 200 nm is used in this embodiment.

In addition, heat treatment is performed for 1 to 12 hours at 300 to 450C in an atmosphere containing between 3 and 100% hydrogen, performinghydrogenation. This process is one of hydrogen termination of danglingbonds in the semiconductor film by hydrogen which is thermally excited.Plasma hydrogenation (using hydrogen activated by a plasma) may also beperformed as another means of hydrogenation.

Note that the hydrogenation processing may also be inserted during theformation of the first interlayer insulating film 338. Namely, hydrogenprocessing may be performed as above after forming the 200 nm thicksilicon oxynitride film, and then the remaining 800 nm thick siliconoxide film may be formed.

Next, a contact hole is formed in the first interlayer insulating film338 and the gate insulating film 310, and source wirings 339 to 342 anddrain wirings 343 to 345 are formed. In this embodiment, this electrodeis made of a lamination film of three-layer structure in which atitanium film having a thickness of 100 nm, an aluminum film containingtitanium and having a thickness of 300 nm, and a titanium film having athickness of 150 nm are continuously formed by a sputtering method. Ofcourse, other conductive films may be used.

A first passivation film 346 is formed next with a thickness of 50 to500 nm (typically between 200 and 300 nm). A 300 nm thick siliconoxynitride film is used as the first passivation film 346 in thisembodiment. This may also be substituted by a silicon nitride film.

Note that it is effective to perform plasma processing using a gascontaining hydrogen such as H₂ or NH₃ etc. before the formation of thesilicon oxynitride film. Hydrogen excited by this pre-process issupplied to the first interlayer insulating film 338, and the filmquality of the first passivation film 346 is improved by performing heattreatment. At the same time, the hydrogen added to the first interlayerinsulating film 338 diffuses to the lower side, and the active layerscan be hydrogenated effectively.

Next, as shown in FIG. 6B, a second interlayer insulating film 347 madeof organic resin is formed. As the organic resin, it is possible to usepolyimide, polyamide, acrylic resin, BCB (benzocyclobutene) or the like.Especially, since the second interlayer insulating film 347 is primarilyused for flattening, acrylic resin excellent in flattening properties ispreferable. In this embodiment, an acrylic resin film is formed to athickness sufficient to flatten a stepped portion formed by TFTs. It isappropriate that the thickness is made 1 to 5 μm (more preferably, 2 to4 μm).

Thereafter, a contact hole is formed in the second interlayer insulatingfilm 347 and the first passivation film 346 and then the pixel electrode348 electrically connected to a drain wiring 345 is formed. In thisembodiment, an indium tin oxide film (ITO) is formed to a thickness of110 nm and patterned to form a pixel electrode. In addition, a compoundof indium oxide and zinc oxide (ZnO) of 2-20% or a compound of zincoxide and gallium oxide also can be used as a transparent electrode.This pixel electrode becomes an anode of an EL element.

Then, as illustrated in FIG. 6C, a bank a (349 a) and a bank b (349 b)formed of a resin material are formed. The bank a (349 a) and the bank b(349 b) are formed by laminating and patterning acrylic resin films,polyimide films, or the like at a thickness of 1 to 2 μm in total. It isto be noted that the material of the film for forming the bank a (349 a)is required to have a higher etching rate than that of the film forforming the bank b (349 b) with regard to the same etchant. Asillustrated in FIG. 6, the bank a (349 a) and the bank b (349 b) areformed between pixels so as to be stripe-like. Though they are formedalong a source wiring 341 in this embodiment, they may be formed along agate wiring 337.

Then, an EL layer 350 is formed by the thin film forming method asdescribed with reference to FIG. 1. It is to be noted that, though onlyone pixel is illustrated here, actually, EL layers corresponding to R(red), G (green), and B (blue), respectively, are formed as illustratedin FIG. 1.

First, an EL material contained in the sample boat is vaporized byresistance heating using the electrode to be the EL material in a vaporstate. The EL material in a vapor state is, after being chargedintentionally, discharged. The discharged EL material in a vapor stateis, after being passed through the mask to which voltage is applied,deposited on the pixel portion on the substrate 110. It is to be notedthat when the EL material in a vapor state is passed through the mask,the direction of progress of the EL material in a vapor state iscontrolled by an electric field around the mask.

In this embodiment, first, by discharging from the sample boat a red ELmaterial as an EL material in a vapor state, a pixel column that emitsred light is formed on the pixels. Then, after the mask is moved in alateral direction, a green EL material is deposited by evaporation fromthe sample boat to form a pixel column that emits green light. The maskis further moved in the lateral direction and a blue EL material isdeposited by evaporation from the sample boat to form a pixel columnthat emits blue light.

As described in the above, by depositing in three installments the pixelcolumns emitting red, green, and blue light, respectively, while movingthe mask, the stripe-like EL layers of three colors are formed.

It is to be noted that, though only one pixel is illustrated in thisembodiment, EL layers emitting the same color are simultaneously formedhere.

It is to be noted that, in this embodiment, Alq as a host material witha red fluorescent pigment DCM doped therein is used as the EL materialfor forming a red EL layer, Alq which is a complex of aluminum and8-hydroxyquinoline is used as the green emitting EL layer, and a complexof zinc and benzoxazole (Zn(oxz)₂) is used as the blue emitting ELlayer, all at a thickness of 50 nm.

A known material can be used as the EL material 350. Taking intoconsideration the driving voltage, such a known material is preferablyan organic material. It is to be noted that, though the EL layer 350 isof a single layer structure having only the above EL layer in thisembodiment, it may be provided with an electron injection layer, anelectron transmission layer, a hole transmission layer, a hole injectionlayer, an electron blocking layer, or a hole element layer, ifnecessary. Further, though a case where an MgAg electrode is used as acathode 351 of the EL element is described in this embodiment, otherknown materials may also be used.

Further, though the EL layers are deposited with regard to each color,the electron injection layer, the electron transmission layer, the holetransmission layer, the hole injection layer, the electron blockinglayer, or the hole element layer in the EL layer may be formedsimultaneously by, for example, spin coating or evaporation of the samematerial irrespective of the color of the EL layer.

After the EL layer 350 is formed, the cathode (MgAg electrode) 351 isformed by vacuum evaporation. It is to be noted that the thickness ofthe EL layer 350 is preferably 80 to 200 nm (typically 100 to 120 nm)and the thickness of the cathode 351 is preferably 180 to 300 nm(typically 200 to 250 nm).

Further, a protective electrode 352 is provided on the cathode 351. Asthe protective electrode 352, a conductive film comprising aluminum asthe main component may be used. The protective electrode 352 may beformed by vacuum evaporation using a mask.

Finally, a second passivation film 353 of a silicon nitride film isformed at a thickness of 300 nm. Though, actually, the protectiveelectrode 352 protects the EL layer from moisture and the like, byfurther forming the second passivation film 353, the reliability of theEL element can be further enhanced.

FIG. 7 illustrates the cross section of an n-channel TFT for switchingas a TFT in the pixel portion.

First, with regard to the TFT for switching illustrated in FIG. 7, FIG.7A illustrates a structure where LDD regions 15 a to 15 d are providedso as not to overlap the gate electrodes 19 a and 19 b through a gateinsulating film 18. Such a structure is very effective in decreasing theoff current value.

On the other hand, these LDD regions 15 a to 15 d are not provided in astructure illustrated in FIG. 7B. In the case that the structureillustrated in FIG. 7B is formed, since the number of the processessteps can be decreased compared with the case where the structureillustrated in FIG. 7A is formed, the production efficiency can beimproved.

In this embodiment, both of the structures illustrated in FIG. 7A andFIG. 7B may be used as the TFT for switching.

FIG. 8 illustrates the cross sectional structure of an n-channel TFT forcontrolling electric current as a TFT in the pixel portion.

In a TFT for controlling electric current illustrated in FIG. 8A, an LDDregion 33 is provided between a drain region 32 and a channel formingregion 34. Though a structure where the LDD region 33 overlaps a gateelectrode 35 through the gate insulating film 18 is illustrated here,the structure may be as illustrated in FIG. 8B where the LDD region 33is not provided.

The TFT for controlling electric current not only supplies electriccurrent for making an EL element emit light but also controls the amountof the supply to make gray-scale display possible. Therefore, it isnecessary to take measures against deterioration due to hot carrierinjection so as to prevent such deterioration even when electric currentis caused to flow.

With regard to deterioration due to hot carrier injection, it is knownthat a structure where an LDD region overlaps a gate electrode is veryeffective. Therefore, the structure where the LDD region overlaps thegate electrode 35 through the gate insulating film 18 as illustrated inFIG. 8A is appropriate. Here, as an off current measure, a structure inwhich part of the LDD region does not overlap the gate electrode isillustrated. However, it is not necessarily required that part of theLDD region does not overlap the gate electrode. Further, depending onthe situation, as illustrated in FIG. 8B, such an LDD region may not beprovided.

In the case of this embodiment, as illustrated in FIG. 6C, the activelayer of the n-channel TFT 205 includes a source region 355, a drainregion 356, an LDD region 357, and a channel forming region 358. The LDDregion 357 overlaps the gate electrode 312 through the gate insulatingfilm 310.

The LDD region is formed only on the side of the drain region, so as notto lower the operation speed. Further, with regard to the n-channel TFT205, while it is not necessary to consider the off current much, theoperation speed is important. Therefore, it is desirable that the LDDregion 357 completely overlaps with the gate electrode to make theresistance component as small as possible. In other words, it ispreferable that there is no so-called offset.

In this way, the active matrix substrate having the structure asillustrated in FIG. 6C is completed. It is to be noted that tocontinuously go through processes steps after a bank 349 is formed untila passivation film 353 is formed without exposing the device to theatmosphere using a multi-chamber-type or in-line-type thin film formingdevice is effective.

By the way, by arranging optimally structured TFTs not only in the pixelportion but also in the driver circuit portion, an active matrixsubstrate according to this embodiment is extremely reliable, and itsperformance characteristics can be improved.

First, a TFT structured to decrease hot carrier injection while caringnot to lower the operation speed as much as possible is used as then-channel TFT 205 of the CMOS circuit forming the driver circuitportion. It is to be noted that the driver circuit as referred to hereinincludes a shift register, a buffer, a level shifter, a sampling circuit(a sample-and-hold circuit), and the like. In the case that digitaldriving is performed, a signal conversion circuit such as a D/Aconverter may further be included.

It is to be noted that, actually, after the process step illustrated inFIG. 6C is completed, the device is preferably packaged (enclosed) in acovering material such as airtight glass, quartz, or plastic such thatthe device is not exposed to the outside air. In this case, ahygroscopic agent such as barium oxide or an antioxidant is preferablydisposed inside the covering material.

After the airtightness is enhanced by processing such as the packaging,a connector (a flexible printed circuit: an FPC) for connectingterminals led from elements or circuits formed on the insulator toexternal signal terminals is attached to complete the device as aproduct. The device in this state, i.e., in a shippable state is hereinreferred to as an EL display device (or an EL module).

Here, the structure of the active matrix EL display device according tothis embodiment is described with reference to a perspective view ofFIG. 9. The active matrix EL display device according to this embodimentincludes a pixel portion 602, a gate side driver circuit 603, and asource side driver circuit 604 formed on a glass substrate 601. A TFT605 for switching in the pixel portion is an n-channel TFT, and isdisposed at an intersection of a gate wiring 606 connected to the gateside driver circuit 603 and a source wiring 607 connected to the sourceside driver circuit 604. A drain of the TFT 605 for switching isconnected to a gate of a TFT 608 for controlling electric current.

Further, a source side of the TFT 608 for controlling electric currentis connected to a power supply line 609. In a structure as thisembodiment, the power supply line 609 has a ground potential (an earthpotential). Further, a drain of the TFT 608 for controlling electriccurrent is connected to an EL element 610. Predetermined voltage (3 to12 V, preferably 3 to 5 V) is applied to an anode of the EL element 610.

Further, an FPC 611 to be an external input/output terminal is providedwith connection wirings 612 and 613 for transmitting a signal to adriver circuit portion, and a connection wiring 614 connected to thepower supply line 609.

FIG. 10 illustrates an example of a circuit structure of the EL displaydevice illustrated in FIG. 9. The EL display device according to thisembodiment has a source side driver circuit 801, a gate side drivercircuit (A) 807, a gate side driver circuit (B) 811, and a pixel portion806. It is to be noted that the driver circuit portion as used herein isa generic name and includes the source side driver circuit and the gateside driver circuits.

The source side driver circuit 801 is provided with a shift register802, a level shifter 803, a buffer 804, and a sampling circuit (asample-and-hold circuit) 805. The gate side driver circuit (A) 807 isprovided with a shift register 808, a level shifter 809, and a buffer810. The gate side driver circuit (B) 811 is similarly structured.

Here, the driving voltage of the shift registers 802 and 808 is 5 to 16V (representatively 10 V). For an n-channel TFT used in a CMOS circuitforming the circuit, the structure denoted as 205 in FIG. 6C issuitable.

Similarly to the case of the shift registers, for the level shifters 803and 809 and the buffers 804 and 810, a CMOS circuit including then-channel TFT 205 illustrated in FIG. 6C is suitable. It is to be notedthat to make the gate wirings have a multi-gate structure such as adouble-gate structure or a triple-gate structure is effective inimproving the reliability of the respective circuits.

In the pixel portion 806, pixels structured as illustrated in FIG. 5 arearranged.

It is to be noted that the above structure can be easily realized bymanufacturing the TFTs in accordance with the manufacturing processillustrated in FIGS. 4 to 6. Further, though only the structure of thepixel portion and the driver circuit portion are illustrated in thisembodiment, according to the manufacturing process of this embodiment,other logic circuits such as a signal division circuit, a D/A convertercircuit, an operational amplifier circuit, and a y correction circuitcan also be formed on the same insulator. Further, it is expected that amemory portion, a microprocessor, and the like can also be formed.

Further, the EL module according to this embodiment including a coveringmaterial is described with reference to FIGS. 11A and 11B. The referencenumerals used in FIGS. 9 and 10 are also used here, if necessary.

FIG. 11A is a top view showing a sealing structure added to a stateillustrated in FIG. 9. Reference numerals 602, 603, and 604 shown bydotted lines denote a pixel portion, a gate side diver circuit, and asource side driver circuit, respectively. The sealing structureaccording to the present embodiment is a structure provided with acovering material 1101 and a sealing material (not shown) for the stateillustrated in FIG. 9.

FIG. 11B is a sectional view taken along the line A-A′ of FIG. 11A. Itis to be noted that the same reference numerals denote the samecomponents in FIGS. 11A and 11B.

As illustrated in FIG. 11B, the pixel portion 602 and the gate sidedriver circuit 603 are formed on the substrate 601. The pixel portion602 is formed of a plurality of pixels each composed of the TFT 202 forcontrolling electric current and the pixel electrode 348 electricallyconnected thereto. The gate side driver circuit 603 is formed using aCMOS circuit where the n-channel TFT 205 and the p-channel TFT 206 arecomplementary combined.

The pixel electrode 348 functions as an anode of the EL element. Thebank a (349 a) and the bank b (349 b) are formed in gaps between thepixel electrodes 348. The EL layer 350 and the cathode 351 are formedinside the bank a (349 a) and the bank b (349 b). Further, theprotective electrode 352 and the second passivation film 353 are formedthereon. Of course, as described in the above, the structure of the ELelement may be reversed and the pixel electrode may be the cathode.

In this embodiment, the protective electrode 352 also functions as awiring common in a pixel column, and is electrically connected to theFPC 611 via the connection wiring 612. Further, all elements included inthe pixel portion 602 and the gate side driver circuit 603 are coveredwith the second passivation film 353. Though the second passivation film353 may be omitted, it is preferable to provide it so that therespective elements are shielded from the external.

The covering material 1101 is adhered by a sealing material 1104. It isto be noted that spacers of a resin film may be provided to secure thespace between the covering material 1101 and a light-emitting element.It is to be noted that the inside 1103 of the sealing material 1104 is asealed space filled with an inert gas such as nitrogen or argon.Further, it is also effective to provide a hygroscopic agent representedby barium oxide inside the sealed space 1103.

Further, it is also possible to provide a filler in the space 1103. Asthe filler, PVC (polyvinyl chloride), an epoxy resin, a silicon resin,PVB (polyvinyl butyral), or EVA (ethylene vinyl acetate) can be used.

In this embodiment, as the covering material 1101, glass, plastic, orceramics can be used.

As the sealing material 1104, though a photo-curable resin is preferablyused, if the heat resistance of the EL layer permits, a thermosettingresin may also be used. It is to be noted that the sealing material 1104is preferably a material that transmits moisture and oxygen as less aspossible. Further, a hygroscopic agent may be added and placed insidethe sealing material 1104.

By encapsulating the EL element using the above method, the EL elementcan be completely shielded from the external, and substances such asmoisture and oxygen which invite deterioration of the EL layer due tooxidation can be prevented from entering. Accordingly, an EL displaydevice with high reliability can be manufactured. It is to be notedthat, though a case where the three kinds of stripe-like EL layers thatemit red, green, and blue light, respectively, are formed in alongitudinal direction is described in this embodiment, they may beformed in a lateral direction.

It is to be noted that the structure of this embodiment can be freelycombined with the structures of Embodiments 1 to 3.

Embodiment 5

When an active matrix type EL display device is placed as illustrated inFIG. 11A, pixel columns may be formed in a longitudinal direction so asto be stripe-like, or, may be formed into a delta arrangement.

Here, a case where red, green, and blue pixels are formed so as to bestripe-like on a substrate is described. It is to be noted that thenumber of colors of the pixels is not necessarily required to be three,and may be one or two. Further, the colors are not limited to these red,green, and blue, and other colors such as yellow, orange, and gray mayalso be used.

It is to be noted that the positional relationship between thesubstrate, a sample boat containing an EL material therein, and a maskfor controlling the EL material in a vapor state is as illustrated inFIG. 1A.

First, an EL material for a red EL layer contained in the sample boat isvaporized, and the EL material in a vapor state is discharged from thesample boat. Here, since predetermined voltage is applied to the mask,the discharged EL material in a vapor state is controlled by an electricfield when it reaches the mask, passes through the mask, and reach adesired location at the pixel portion. In this way, deposition at adesired location in the pixel portion can be controlled. The voltageapplied to the mask is equal to or more than several 10 V and equal toor less than 10 kV.

First, the red EL material is deposited through evaporation. Sincevoltage is applied to the mask, the EL material can be selectivelydeposited at a desired location in the pixel portion.

As the mask for forming a stripe-like EL layer in a pixel portion 704(see FIG. 13A), a mask 500 for stripes illustrated in FIG. 12A may beused. It is to be noted that, as the mask, a mask which can form pixelsinto a delta arrangement may also be used.

In this embodiment, first, the red EL material is deposited throughevaporation using the mask 500 for stripes illustrated in FIG. 12A.Then, after the mask 500 for stripes is moved in a lateral direction ofan arrow i by one pixel column, a green EL material is deposited. Afterthat, the mask 500 is further moved in the lateral direction of thearrow i by one pixel column, and then, a blue EL material is deposited.In this way, stripe-like red, green, and blue EL layers are formed inthe pixel portion.

It is to be noted that, by forming the red, green, and blue EL materialsin the pixel portion using the mask, stripe-like pixels can be formed inthe pixel portion as illustrated in FIG. 13A.

The mask 500 for stripes illustrated in FIG. 12A may be used as a maskfor forming stripe-like EL layers in the pixel portion 704, while a mask501 for a delta arrangement illustrated in FIG. 12B may be used as amask for forming pixels into a delta arrangement.

In FIG. 13A, an EL layer 704 a emitting red light, an EL layer 704 bemitting green light, and an EL layer 704 c emitting blue light areformed. It is to be noted that banks (not shown) are formed over sourcewirings through an insulating film in a longitudinal direction along thesource wiring so as to be stripe-like.

The EL layer herein refers to a layer of an organic EL material thatcontributes to light emission such as an EL layer, a charge injectionlayer, or a charge transmission layer. There may be a case where the ELlayer is a single EL layer. On the other hand, when a hole injectionlayer an EL layer are laminated, for example, the laminated films as awhole is referred to as an EL layer.

Here, it is desirable that a mutual distance (D) of adjacent pixels ofthe same color in a line is five or more times (preferably ten or moretimes) as large as the film thickness (t) of the EL layer. This isbecause, if D<5t, there is a possibility that a problem of crosstalk iscaused between pixels. It is to be noted that, since an image with highdefinition can not be obtained if the distance (D) is too large, it ispreferable that the relationship of 5t<D<50t (preferably 10t<D<35t) issatisfied.

Further, the EL layer may be formed such that stripe-like banks areformed in a lateral direction and EL layers emitting red, green, andblue light may be formed in the lateral direction respectively. Here,the banks (not shown) are formed over gate wirings through an insulatingfilm along the gate wiring.

In this case, also, it is desirable that a mutual distance (D) ofadjacent pixels of the same color in a line is five or more times(preferably ten or more times) as large as the film thickness (t) of theEL layer. More preferably, the relationship of 5t<D<50t (preferably10t<D<35t) is satisfied.

As in this embodiment, by electrically controlling an EL material in avapor state when an EL layer is formed by evaporation, the location ofdeposition can be controlled.

It is to be noted that the structure of this embodiment can be freelycombined with the structures of Embodiments 1 to 4.

Embodiment 6

A case of using the present invention in a passive type (simple matrixtype) EL display device is explained in Embodiment 6. FIG. 14 is used inthe explanation. In FIG. 14, reference numeral 1301 denotes a substratemade of plastic, and 1302 denotes an anode made of a transparentconductive film. In Embodiment 6, as the transparent conductive film, acompound of indium oxide and zinc oxide is formed by an evaporationmethod. Note that, although not shown in FIG. 14, a plurality of anodesare arranged in a stripe shape, in a parallel direction with a definedspace.

Further, banks made of a bank a (1303 a) and a bank b (1303 b) areformed so as to fill up the space between the cathodes 1305 arranged inthe stripe shape in a perpendicular direction to the defined space.

Subsequently, EL layers 1304 a to 1304 c made of an EL material areformed by the evaporation method shown in FIG. 1. Note that referencenumeral 1304 a is an EL layer emitting red color, 1304 b is an EL layeremitting green color, and 1304 c is a light emitting layer emitting bluecolor. The organic EL material used may be similar to that used inEmbodiment 1. The EL layers are formed along grooves, which are formedby the bank a (1303 a) and bank b (1303 b), and therefore are arrangedin a stripe shape, in a perpendicular direction to the defined space.

Note that, in Embodiment 6, the position where an EL material is coatedon an anode is controlled by using a mask, and it may further becontrolled by applying a voltage to an anode.

Next, although not shown by FIG. 14, a plurality of cathodes and aplurality of protective electrodes which have longitudinal directions ina perpendicular direction with the defined space, are arranged in astripe shape orthogonal to the anodes 1302. Note that the cathodes 1305are made of MgAg, and that the protective electrodes 1306 are aluminumalloy films in Embodiment 6, and both are formed by the evaporationmethod. Further, although not shown in the figure, a wiring is extendedto a portion in which an FPC is later attached so as to apply apredetermined voltage to the protective electrodes 1306.

Further, after forming the protective electrodes 1306, not shown in thefigure, a silicon nitride film may be formed here as a passivation film.

An EL element is thus formed on the substrate 1301. Note that the lowerside electrodes are transparent anodes in Embodiment 6, and thereforelight emitted from the EL layers 1304 a to 1304 c is emitted to thelower surface (the substrate 1301). However, the EL element structurecan be inverted and the lower electrodes can be made into lightshielding cathodes. In that case, light emitted from the EL layers 1304a to 1304 c is irradiated to an upper surface (an opposite side to thesubstrate 1301).

Next, a ceramic substrate is prepared as a covering material 1307. Aceramic substrate is used because the covering material may be lightshielding with the structure of this embodiment, but of course asubstrate made from plastic or glass may also be used for a case ofinverted EL element structure stated above since the covering materialshould be transparent.

After thus preparing the covering material 1307, it is joined with asealing material 1309 made of an ultraviolet hardening resin. It is tobe noted that the inside 1308 of the sealing material 1309 is a sealedspace filled with an inert gas such as nitrogen or argon. Further, it isalso effective to provide a hygroscopic agent represented by bariumoxide in the sealed space 1308. Lastly, an anisotropic conducting film(FPC) 1311 is attached, and the passive type EL display device iscompleted.

Note that it is possible to implement the constitution of Embodiment 6by freely combining it with the constitution of any of Embodiments 1 to5.

Embodiment 7

When the present invention is implemented to manufacture an activematrix EL display device, it is effective to use a silicon substrate(silicon wafer) as a substrate. In the case of using the siliconsubstrate as the substrate, a manufacturing technique of MOSFET utilizedin the conventional IC, LSI or the like can be employed to manufacture aswitching element and a current control element to be formed in thepixel portion, or a driver element to be formed in the driver circuitportion.

The MOSFET can form circuits having extremely small variations as in itsachievements in the IC and the LSI. Particularly, it is effective forthe active matrix EL display device with an analog driver of performinggradation display by an electric current value.

It is to be noted that the silicon substrate is not transmissive, andtherefore the structure needs to be constructed so that light from theEL layer is irradiated to a side opposite to the substrate. Thestructure of the EL display device of Embodiment 7 is similar to that ofFIG. 14. However, the difference is that the MOSFET is used for forminga pixel portion 602 and a driver circuit portion 603 instead of a TFT.

Note that it is possible to implement the constitution of Embodiment 7by freely combining it with the constitution of any of Embodiments 1 to6.

Embodiment 8

An EL display device formed by implementing the present invention hassuperior visibility in bright locations in comparison to a liquidcrystal display device because it is a self-emissive type device, andmoreover its field of vision is wide. Accordingly, it can be used as adisplay portion for various electric apparatuses. For example, it isappropriate to use the EL display device of the present invention as adisplay portion of an EL display (a display incorporating the EL displaydevice in its casing) having a diagonal equal to 30 inches or greater(typically equal to 40 inches or greater) for appreciation of TVbroadcasts by large screen.

Note that all displays exhibiting (displaying) information such as apersonal computer display, a TV broadcast reception display, or anadvertisement display are included as the EL display. Further, the ELdisplay device of the present invention can be used as a display portionof the other various electric apparatuses.

The following can be given as examples of such electric apparatuses: avideo camera; a digital camera; a goggle type display (head mounteddisplay); a car navigation system; an audio reproducing device (such asa car audio system, an audio compo system); a notebook personalcomputer; a game equipment; a portable information terminal (such as amobile computer, a mobile telephone, a mobile game equipment or anelectronic book); and an image playback device provided with a recordingmedium (specifically, a device which performs playback of a recordingmedium and is provided with a display which can display those images,such as a digital video disk (DVD)). In particular, because portableinformation terminals are often viewed from a diagonal direction, thewideness of the field of vision is regarded as very important. Thus, itis preferable that the EL display device is employed. Examples of theseelectric apparatuses are shown in FIGS. 15 to 16.

FIG. 15A is an EL display, containing a casing 2001, a support stand2002, and a display portion 2003. The present invention can be used inthe display portion 2003. Since the EL display is a self-emissive typedevice without the need of a backlight, its display portion can be madethinner than a liquid crystal display device.

FIG. 15B is a video camera, containing a main body 2101, a displayportion 2102, an audio input portion 2103, operation switches 2104, abattery 2105, and an image receiving portion 2106. The EL display deviceof the present invention can be used in the display portion 2102.

FIG. 15C is a portion of a head fitting type EL display (right side),containing a main body 2201, a signal cable 2202, a head fixing band2203, a display portion 2204, an optical system 2205, and an EL displaydevice 2206. The present invention can be used in the EL display device2206.

FIG. 15D is an image playback device (specifically, a DVD playbackdevice) provided with a recording medium, containing a main body 2301, arecording medium (such as a DVD) 2302, operation switches 2303, adisplay portion (a) 2304, and a display portion (b) 2305. The displayportion (a) is mainly used for displaying image information, and theimage portion (b) is mainly used for displaying character information,and the EL display device of the present invention can be used in theimage portion (a) and in the image portion (b). Note that domestic gameequipment is included as the image playback device provided with arecording medium.

FIG. 15E is a mobile computer, containing a main body 2401, a cameraportion 2402, an image receiving portion 2403, operation switches 2404,and a display portion 2405. The EL display device of the presentinvention can be used in the display portion 2405.

FIG. 15F is a personal computer, containing a main body 2501, a casing2502, a display portion 2503, and a keyboard 2504. The EL display deviceof the present invention can be used in the display portion 2503.

Note that in the future if the emission luminance of organic ELmaterials becomes higher, the projection of light including outputtedimages can be enlarged by lenses or the like. Then it will becomepossible to use the EL display device of the present invention in afront type or a rear type projector.

The above electric apparatuses are becoming more often used to displayinformation provided through a telecommunication path such as theInternet or CATV (cable television), and in particular, opportunitiesfor displaying animation information are increasing. The response speedof organic EL materials is extremely high, and therefore the EL displaydevice is favorable for performing animation display. However, thecontours between pixels become hazy, whereby the entire animation alsobecomes hazy. Accordingly, it is extremely effective to use the ELdisplay device of the present invention in the display portion ofelectric apparatuses because of its capability of clarifying thecontours between pixels.

Further, the emitting portion of the EL display device consumes power,and therefore it is preferable to display information so as to have theemitting portion become as small as possible. Therefore, when using theEL display device in a display portion which mainly displays characterinformation, such as a portable information terminal, in particular, aportable telephone and an audio reproducing device, it is preferable todrive it by setting non-emitting portions as background and formingcharacter information in emitting portions.

FIG. 16A is a portable telephone, containing a main body 2601, an audiooutput portion 2602, an audio input portion 2603, a display portion2604, operation switches 2605, and an antenna 2606. The EL displaydevice of the present invention can be used in the display portion 2604.Note that by displaying character information in emitting portions in ablack background in the display portion 2604, the power consumption ofthe portable telephone can be reduced.

FIG. 16B is an audio reproducing device, specifically a car audiosystem, containing a main body 2701, a display portion 2702, andoperation switches 2703 and 2704. The EL display device of the presentinvention can be used in the display portion 2702. Furthermore, an audioreproducing device for a car is shown in Embodiment 8, but it may alsobe used for a mobile type and a domestic type of audio reproducingdevice. Note that by displaying character information in emittingportions in a black background in the display portion 2704, the powerconsumption can be reduced. This is particularly effective in a mobiletype audio reproducing device.

The range of applications of the present invention is thus extremelywide, and it is possible to apply the present invention to electricapparatuses in all fields. Furthermore, any constitution of the ELdisplay device shown in Embodiments 1 to 7 may be employed in theelectric apparatuses of Embodiment 8.

Embodiment 9

Described with reference to FIGS. 17A and 17B in this embodiment is amethod of controlling an EL material vaporized in a sample boat(hereinafter referred to as an EL material in a vapor state) using anelectric field around a plurality of masks and forming a film of the ELmaterial on a substrate.

In FIG. 17, a reference numeral 1010 denotes a substrate. A sample boat1011 has an EL material contained therein.

Further, the sample boat 1011, a first mask, and a second mask to bedescribed here may be separately provided, or, alternatively, may beintegrally formed as one device.

It is to be noted that, when a red EL layer is to be formed, the sampleboat 1011 contains an EL material that emits red light (hereinafterreferred to as a red EL material). When a green EL layer is to beformed, the sample boat 1011 contains an EL material that emits greenlight (hereinafter referred to as a green EL material). When a blue ELlayer is to be formed, the sample boat 1011 contains an EL material thatemits blue light (hereinafter referred to as a blue EL material).

It is to be noted that, in this embodiment, Alq as a host material witha red fluorescent pigment DCM doped therein is used as the red ELmaterial for forming a red EL layer, Alq that is a complex of aluminumand 8-hydroxyquinoline is used as the green EL material for forming agreen-light-emitting EL layer, and a complex of zinc and benzoxazole(Zn(oxz)₂) is used as the blue EL material for forming ablue-light-emitting EL layer.

It is to be noted that the above EL materials are merely examples andother known EL materials may also be used. Further, though the ELmaterials are selected to emit red, green, and blue light, the presentinvention is not limited thereto and colors such as yellow, orange, andgray may also be used.

In this embodiment, first, the sample boat contains the red EL material.After a red EL layer is formed on the substrate, the sample boat nowcontaining the green EL material is used to form a green EL layer on thesubstrate. Then, finally, the sample boat now containing the blue ELmaterial is used to form a blue EL layer on the substrate.

As described in the above, by depositing through evaporation of the red,green, and blue EL materials in three installments, EL layers can beformed.

First, an EL material contained in the sample boat 1011 is vaporized byresistance heating using an electrode 1020. Just as the EL material in avapor state is discharged from the sample boat 1011, under the influenceof an electric field generated by the electrode 1012 attached at anopening of the sample boat 1011, the EL material in a vapor state ischarged to be charged particles. The direction of progress of thesecharged particles is controlled when they pass through masks by anelectric field around the masks generated by voltage applied to firstblocking portions 1018 and second blocking portions 1019 b.

It is to be noted that an electrode may be provided between the sampleboat 1011 and the mask 1013 to control the charge of the EL material ina vapor state discharged from the sample boat 1011 by an electric fieldgenerated by the electrode.

As a result, the vapor EL material passes through spaces of the firstand second blocking portions to be deposited on the surface of thesubstrate.

In the first mask 1013, the first blocking portions 1018 are a pluralityof conductive wires arranged in parallel with one another (stripe-like)formed of a conductive material such as copper, iron, aluminum,tantalum, titanium, or tungsten, a mesh-like structure, or a plate-likestructure. In a second mask 1019 a, the second blocking portions 1019 bare a plurality of conductive wires arranged in parallel with oneanother (stripe-like) formed of a conductive material such as copper,iron, aluminum, tantalum, titanium, or tungsten, a mesh-like structure,or a plate-like structure. The EL material in a vapor state repels anelectric field generated by negative voltage applied to the firstblocking portions 1018, and thus, passes through the gaps between thefirst blocking portions 1018. Further, the EL material in a vapor staterepels an electric field generated by negative voltage applied to thesecond blocking portions 1019 b, and thus, passes through the gapsbetween the second blocking portions 1019 b to be deposited on thesubstrate.

Though FIGS. 17A and 17B illustrate a case where the sections of thefirst blocking portion and of the second blocking portion are circular,the present invention is not limited thereto, and the sections may berectangular, oval or polygonal.

It is to be noted that voltage for giving the EL material in a vaporstate a potential which repels the first blocking portions 1018 of thefirst mask 1013 is applied to the first blocking portions 1018 of thefirst mask 1013. This allows the EL material to pass through the spacesbetween the first blocking portions 1018 of the first mask 1013. It isto be noted that, here, the EL material in a vapor state is charged bythe electric field generated by the electrode 1012 to which negativevoltage is applied, while negative voltage is applied by an electrode1015 a to the first blocking portions 1018 of the first mask 1013 togenerate an electric field. Further, negative voltage is applied by anelectrode 1015 b to the second blocking portions 1019 b of the secondmask 1019 a to generate an electric field. These make the chargedparticles of the EL material in a vapor state electrically repel thefirst and second blocking portions to pass through gaps of the first andsecond blocking portions.

By making a structure as illustrated in FIG. 17A and by appropriatelycontrolling the negative first voltage applied to the first blockingportions 1018 and the negative second voltage applied to the secondblocking portions 1019 b in the range of several equal to or more than10 V and equal to or less than 10 kV, the location of deposition can becontrolled with high accuracy.

It is to be noted that the distance between the first mask 1013 and thesecond mask 1019 a, the distance between the second mask 1019 a and thesubstrate, the distance between the first blocking portions 1018, thedistance between the second blocking portions 1019 b, and the like canbe appropriately set by those who implement the present invention. Forexample, the distance between the first blocking portions 1018 and thedistance between the second blocking portions 1019 b may be a pixelpitch of the pixel electrode formed over the substrate.

Further, openings in the masks refer to gaps between the first or secondblocking portions.

Further, a surface where an EL material is to be formed herein refers toa part of the surface of a pixel electrode or an organic film where athin film is to be formed.

Further, by applying negative voltage by an electrode 1014 to inner sidesurfaces of an evaporation chamber 1021 which has therein the sampleboat 1011, the first and second masks, and the substrate 1010, thenegatively charged EL material in a vapor state can be made to repel theinner side surfaces of the evaporation chamber, and therefore, the ELmaterial in a vapor state can be deposited without adhering to the innerside surfaces of the evaporation chamber.

By depositing the red EL material in the sample boat 1011 byevaporation, a stripe-like red EL layer is formed on pixels. Here, themask is moved in a direction of an arrow k by one pixel column, and in asimilar way, a green EL material is deposited by evaporation from thesample boat 1011 to form a green EL layer next to the red EL layer. Themask is further moved in the direction of the arrow k by one pixelcolumn and the blue EL material is deposited by evaporation from thesample boat 1011 to form a blue EL layer next to the green EL layer. Inother words, by depositing in three installments pixel columns emittingred, green, and blue light, respectively, as the mask is moved in thedirection of the arrow k, stripe-like EL layers of three colors areformed. It is to be noted that the thickness of the EL layers formedhere is preferably 100 nm to 1 μm.

It is to be noted that the sample boat 1011 having the EL materialcontained therein may be changed every time when the kind of EL materialis changed, or, alternatively, only the EL material to be used may bechanged without changing the sample boat 1011.

It is to be noted that a pixel column as used herein refers to a columnof pixels formed by being partitioned by banks (not shown) that areformed over source wirings. Therefore, a pixel column may also berepresented as a plurality of pixels lined up along a source wiring.Though a case where the banks are formed over the source wirings isdescribed here, the banks may be formed over gate wirings. In that case,a plurality of pixels lined up along a gate wiring is referred to as apixel column.

Therefore, a pixel portion (not shown) may be regarded as an aggregateof a plurality of pixel columns partitioned by stripe-like banksprovided over a plurality of source wirings or a plurality of gatewirings. The pixel portion may also be regarded as constitution of pixelcolumns having stripe-like EL layers emitting red light formed thereon,pixel columns having stripe-like EL layers emitting green light formedthereon, and pixel columns having stripe-like EL layers emitting bluelight formed thereon.

Since the stripe-like banks are provided over the plurality of sourcewirings or the plurality of gate wirings, practically, the pixel portionmay also be regarded as an aggregate of a plurality of pixel columnspartitioned by the plurality of source wirings or the plurality of gatewirings.

Further, it is preferable to apply voltage to a pixel electrode (ananode) formed on the substrate 1010 to generate an electric field thatfurther controls the EL material in a vapor state having passed throughthe first and second masks and selectively deposits the EL material in avapor state at desired locations.

Further, in order to accurately position the first mask 1013 and thesecond mask 1019 a, the first mask 1013 and the second mask 1019 a maybe formed by laminating two conductive plates and cutting themsimultaneously by an electron discharge method to form slit-like orcircular holes.

It is to be noted that the structure of this embodiment can be freelycombined with the structures of Embodiments 1 to 8.

Embodiment 10

According to the present invention, it is also possible to use an ELmaterial that can use phosphorescence from triplet exciton for lightemission (also referred to as a triplet compound). A self-light-emittingdevice using an EL material that can use phosphorescence for lightemission can drastically improve the external light emission quantumefficiency. This makes it possible to lower the power consumption,prolong the life, and lighten the weight, of the EL element.

The following papers report that the external light emission quantumefficiency is improved using triplet exciton.

The structural formula of an EL material (coumarin pigment) reported byT. Tsutsui, C. Adachi, and S. Saito in Photochemical Processes inOrganized Molecular Systems, ed. K. Honda (Elsevier Sci. Pub., Tokyo,1991), p. 437 is as follows:

(Chemical Formula 1)

The structural formula of an EL material (Pt complex) reported by M. A.Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson,and S. R. Forrest in Nature 395 (1998), p. 151 is as follows:

(Chemical Formula 2)

The structural formula of an EL material (Ir complex) reported by M. A.Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson, and S. R. Forrest inAppl. Phys. Lett., 75 (1999), p. 4, and by T. Tsutsui, M. J. Yang, M.Yahiro, K. Nakamura, T. Watanabe, T. Tsuji, Y. Fukuda, T. Wakimoto, andS. Mayaguchi in Jpn. Appl. Phys., 38 (12B) (1999) L1502 is as follows:

(Chemical Formula 3)

If the above phosphorescence from triplet exciton can be used, inprinciple, external light emission quantum efficiency that is three tofour times as much as that when fluorescence from singlet exciton isused can be realized.

It is to be noted that the structure of this embodiment can be freelycombined with any structures of Embodiments 1 to 9.

According to the present invention, when a film of an EL material isformed by evaporation through a mask on a surface where it is to beformed, a situation in which the EL material can not pass through themask and is deposited on the mask can be avoided. Further, according tothe present invention, the accuracy of positioning the location of filmformation can be improved by using a plurality of masks.

Further, since the EL material is prevented from being deposited on themask by electric repellence, the mask can be used many times. Further, afilm of the EL material can be formed with accuracy without a problem ofinaccurate positioning. Therefore, the manufacturing yield of an ELdisplay device using the EL material can be improved and the cost can belowered. Further, since a location of deposition of the EL material in avapor state is controlled just before the deposition, a conventionaldeposition method can be used, and the present invention can be appliedwidely.

1. A method of forming a thin film, wherein a sample boat having an EL material contained therein, a substrate having an electrode provided thereon, and a mask between the sample boat and the substrate are provided, wherein the EL material is made to be in a vapor state in the sample boat, wherein the EL material is in the vapor state is discharged from the sample boat toward the substrate, and wherein the EL material in the vapor state is made to pass through an opening of the mask corresponding to the electrode to deposit the EL material on the electrode on the substrate and form a thin film.
 2. A method of forming a thin film as claimed in claim 1, wherein voltage is applied to the mask.
 3. A method of forming a thin film as claimed in claim 1, wherein the EL material in a vapor state is charged when the EL material is made to be in a vapor state in the sample boat and the EL material in a vapor state is discharged from the sample boat toward the substrate.
 4. A method of forming a thin film as claimed in claims 1, wherein the opening in the mask is a gap of blocking portions.
 5. A method of forming a thin film as claimed in claim 1, wherein there are a plurality of the masks and different voltages are applied to the respective plurality of masks.
 6. A method of forming a thin film as claimed in claim 1, wherein the electrode is a pixel electrode.
 7. A method of forming a thin film as claimed in claim 1, wherein the EL material is a low molecular weight material.
 8. A method of forming a thin film as claimed in claim 1, wherein the thickness of the thin film is 10 nm to 10 μm.
 9. A method of forming a thin film as claimed in claim 1, wherein the mask is a conductive wire formed of a conductive material, a mesh-like structure formed of conductive wires, a plate-like structure formed of a conductive material, or a plurality of conductive wires arranged in parallel with one another.
 10. A self-light-emitting device manufactured using a method of forming a thin film as claimed in claim
 1. 11. A thin film forming device comprising: a sample boat having an EL material contained therein; means for making the EL material in a vapor state in the sample boat; a substrate having an electrode provided thereon; a mask between the sample boat and the substrate; and means for applying voltage to the mask.
 12. A thin film forming device as claimed in claim 11, wherein a direction of progress or a location of deposition of the EL material in the vapor state is controlled by the means for applying voltage to the mask.
 13. A thin film forming device as claimed in claim 11, further comprising means for charging the EL material in the vapor state.
 14. A thin film forming device as claimed in claim 11, by further comprising another mask provided between the substrate and the mask, and voltage which is different from that applied to the mask is applied to the another mask.
 15. A method of forming a thin film, wherein a sample boat having an EL material contained therein, a substrate having an electrode provided thereon, and a mask between the sample boat and the substrate are provided, wherein the EL material is made to be in a vapor state in the sample boat, wherein the EL material is in the vapor state is discharged from the sample boat toward the substrate, wherein the EL material in the vapor state is made to pass through an opening of the mask corresponding to the electrode to deposit the EL material on the electrode on the substrate and form a thin film, and wherein voltage is applied to the mask.
 16. A method of forming a thin film, wherein a sample boat having an EL material contained therein, a substrate having an electrode provided thereon, and a mask between the sample boat and the substrate are provided, wherein the EL material is made to be in a vapor state in the sample boat, wherein the EL material is in the vapor state is discharged from the sample boat toward the substrate, wherein the EL material in the vapor state is made to pass through an opening of the mask corresponding to the electrode to deposit the EL material on the electrode on the substrate and form a thin film, and wherein the EL material in the vapor state is charged.
 17. A thin film forming device comprising: a sample boat having an EL material contained therein; means for making the EL material in a vapor state in the sample boat; a substrate having an electrode provided thereon; a mask between the sample boat and the substrate; means for applying voltage to the mask; and means for charging the EL material in the vapor state. 